I ran some more tests based on the suggestions here. The test vehicle still gained 387 lbs from Automation to Beam with only the driver’s seat, so passengers aren’t included. I can’t find any options that would add weight in Beam. Fuel is indeed magical and weightless and fixtures did account for a bit of that weight, but only 14 lbs. Probably a quirk of the exporter/scaling error at this point unless there are any new ideas.